The dwindling supplies of high grade petroleum feedstocks necessitates the increased production and processing of transportation fuels from lower grade, heavy petroleum feedstocks and synthetic liquid hydrocarbons derived from hydrocarbon-containing, or precursor hydrocarbon-containing, solids. It has become necessary to process whole heavy petroleum crudes and residua from unconventional sources, and synthetic fuels (syncrudes; e.g. liquified coal, oil from coal carbonization, oil from tar sands, shale oil and the like inclusive of residua or viscous syncrude fractions) are under active consideration as commercial feedstock replacements for petroleum. Many of the hydrocarbons from these sources contain very fine particulate solids (e.g., sand, clays, oil shale, coal ash, carbonaceous particles and the like) in concentrations which must be removed before such materials can be employed as feedstocks in conventional refining operations.
The presence of the finely divided solids, particulates, or dusts, in such liquids presents a major problem in processing hydrocarbons from these sources. For example, in shale oil, recovered from oil shale in situ or ex situ, extremely finely divided shale solids are concentrated in the shale oil, particularly in the heavy shale oil fractions. Thus, the oil produced by retorting oil shale is frequently contaminated with shale fines, the amount and characteristics of which may vary widely, and are a function of both the source of oil shale and the retorting process used. For example, oil produced from Colorado shale by a surface retorting process typically contains from about 2 to about 6 weight percent of approximately 5 micron mean diameter relatively non-porous particles. In contrast, oil produced from a surface retorted Australian shale typically contains from about 8 to about 16 weight percent of approximately 4 micron mean diameter particles, many of which are porous and some non-porous. Shale oils as a class present very difficult solids separation problems. Many shale oils contain non-porous solids carbonates, and others contain porous clay based materials, or both. The clay based solids may present added separation problems as contrasted with those containing predominately carbonate solids, and such shale oils often generally contain very high solids concentrations. The concentration of solids in such fractions often ranges as high as about 8 percent or 10 percent, often even as high as 16 percent, and higher. These solids, major portions of which typically range in size from about 0.5 micron to about 5 microns, often from about 1 micron to about 4 microns, are extremely difficult to remove from the shale oil. Moreover, the shale oil contains high concentrations of olefinic compounds, these reacting with one another or other compounds to form gums, or high molecular weight polymers, this adding to the difficulty of separating water and solids from the shale oil. Such materials interfere with refinery operations by clogging catalysts, coating process equipment, heat exchange surfaces, and the like. Conventional filtration and centrifugation process per se are simply inadequate for dedusting, or removing the gums and particulate solids from shale oil, or other types of low grade heavy petroleum feedstocks and syncrudes, especially heavy oil fractions and residua. Equipment and processing costs are horrendous, and loss of oil is one of the largest process debits. Waste disposal problems created by the necessity of disposing of oil wet solids adds to the burden.
It is conventional to "desalt" petroleum crudes to remove water and salts. In a typical desalting process, a surface active agent and water are often added to the petroleum crude, passed through a mixer to form an emulsion, and the emulsion then heated and passed to a desalting vessel, or staged series of such vessels. In a desalting vessel, technically termed an electrostatic coalescer, the emulsion is subjected to a high voltage electrostatic field to cause droplets of water to coalesce and form separate phases; a water phase and a clean oil phase separated by an emulsion phase. A low salt, essentially water-free oil phase forms as an upper stratum, and a salt-containing aqueous phase forms as a bottom stratum, with an emulsion phase located between the clean oil and water strata. The low salt, essentially water free (low BS&W) oil phase is withdrawn from the top of the vessel for refinery processing, and the salt-containing aqueous phase is withdrawn from the bottom of the vessel and discharged as an effluent.
Solids have been removed from shale oil by the addition of water to the shale oil, and the mixture then subjected to an electrostatic field to resolve the mixture into a dedusted shale oil phase, and an aqueous phase which carries the finely divided solids. Reference is made, e.g., to U.S. Pat. No. 3,951,771 which issued on Apr. 20, 1976 to E. D. Burger. In accordance with the Burger process an electrostatic coalescer and centrifuge are employed in combination to remove solids from shale oil which contains low to moderate concentrations of solids. The solids content of the shale oil is reduced in the electrostatic coalescer, but the oil losses present a serious problem. Reference is also made to U.S. Pat. No. 3,929,625 which issued Dec. 30, 1975 to Roy M. Lucas. In accordance with the process described by this reference, a surface active agent and water are admixed with the oil to form an emulsion, and the emulsion is then transferred to an electrostatic coalescer to form a separate clean oil phase and a solids-containing aqueous phase, the former of which is recovered as a feedstock for use in refinery operations. A poly oxyalkylene derived nonionic polymeric surfactant is employed as the surface active agent, exemplary of which are oxypropylated, oxyethylated, polyethylene amine and oxypropylated, oxyethylated butyl phenol formaldehyde resin. Solids removed from shale oil by water washing/electrostatic coalescence, however, has not been particularly effective, and such treatment is particularly ineffective when employed to dedust oils which contain about 6 weight percent solids, or higher. Above this level of solids concentration phase separation within the electrostatic coalescer is not only difficult, but an unacceptably high level of oil is contained in the water effluent. Moreover, the solids content of the water effluent is sufficiently high that flow is difficult due to the extremely high viscosity. Whereas diluents, e.g., naphtha, diesel oil and the like, may be added to the crude oils prior to treatment to reduce the total solids concentration, this necessitates an added step for recovery of the diluent which is a burden on the process.
It is, accordingly, the primary object of the present invention to obviate these and other prior art deficiencies, particularly by providing novel compositions, and process for dedusting unconventional whole heavy petroleum crudes, heavy petroleum crude fractions and residua, syncrudes, syncrude fractions, and syncrude residua.
A particular object is to provide novel compositions, and process for dedusting unconventional whole heavy petroleum crudes, heavy petroleum crude fractions and residua, syncrudes and syncrude fraction which contains above about 6 weight percent finely divided solids, to provide a clean oil product, or product suitable for use in refining operations.
A further, and more particular object is to provide novel compositions useful as additives in the dedusting of shale oil, and process wherein the additive containing shale oil, particularly shale oil which contains above about 6 weight percent finely divided solids, to provide a shale oil effluent suitable for use in refining operations; the use of such additives, or process utilizing such additives, being particularly useful for dedusting a shale oil where it is desired to hydrogenate (or hydrogen treat) a feedstock constituting a major portion or substantially the whole shale oil, or high solids-containing bottoms fraction of the shale oil.
These objects and others are achieved in accordance with the present invention:
(I) A composition useful as a surfactant, which comprises
(A) an ethoxylated or propoxylated ester characterized as follows: ##STR1## where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are selected from (a) ethoxy or propoxy groups, or mixed ethoxy and propoxy groups, and
(b) the de-hydroxylated residue of a fatty acid molecule, or moiety represented by the formula ##STR2## where R is a straight-chain hydrocarbon moiety which can be substituted or unsubstituted, saturated or unsaturated, and where unsaturated can contain conjugated or unconjugated double bonds. The hydrocarbon moiety can thus be exemplified by hydrocarbon groups which range from about 6 to about 30 carbon atoms, preferably from about 8 to about 20 carbon atoms, e.g., alkyl groups such as n-hexyl, n-octyl, n-decyl, n-dodecyl, n-octadecyl, octenyl, 9-octadecenyl, etc. This moiety can be further represented as the de-hydroxylated residue of fatty acids such as caprylic, capric, lauric, myristic, eleostearic, licanic, arachidic, arochidonic, behenic, lignoceric, nisinic and the like.
In the formula, at least one and up to three of R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is ethoxy, propoxy or mixed ethoxy and propoxy groups, and conversely at least one and up to three of R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is the residue of a fatty acid molecule, or moiety represented by the formula RCO--. Ethoxy, propoxy, or mixed ethoxy and propoxy groups, are thus attached through oxygen to form one to three of the 2, 3, 5 or 6 carbon atoms of the 1, 4-sorbitan skeleton, and from one to three of the fatty acid chains are attached through oxygen to the 2, 3, 5 or 6 carbon atoms of the 1, 4-sorbitan skeleton. In other words, all of the R.sub.1, R.sub.2, R.sub.3 and R.sub.4 substituents attached through oxygen to the 2, 3, 5 or 6 carbon atoms are either ethoxy, propoxy or mixed ethoxy/propoxy groups or RCO--groups, and up to three of the substitutents can be ethoxy, propoxy or mixed ethoxy/propoxy groups with the remainder RCO--, or up to three of the substitutents can be RCO-- with the remainder ethoxy, propoxy or mixed ethoxy/propoxy groups. The fatty acid moiety is generally not a pure species but comprised of mixtures of acid moieties. The molecular species is thus not a pure compound, but an admixture of compounds. Within the admixture of compounds, the molecular average of the admixture, or average molecule, preferably contains about three of the ethoxy, propoxy or mixed ethoxy/propoxy chains, and about one fatty acid chain. In an individual R.sub.1, R.sub.2, R.sub.3 or R.sub.4 group, where from one to three of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are ethoxy, propoxy or mixed ethoxy and propoxy groups, the number of ethoxy, propoxy or mixed ethoxy/propoxy groups can range from 1 to about 50, preferably from about 1 to about 25, and more preferably from about 2 to about 10, and the sum total of the ethoxy, propoxy or mixed ethoxy/propoxy groups in the molecule ranges from about 5 to about 50, preferably from about 10 to about 30. The end of the molecule which contains the 1, 4-sorbitan skeleton tends to be water soluble, and the end of the molecule which contains the fatty acid chain tends to be water insoluble. In use, the solids particles in an oil are water wet, and encapsulated by the action of the surfactant, the water droplets being coalesced into larger droplets which settle out with the solids particles.
The surfactant is preferably constituted of an admixture of said ethoxylated or propoxylated ester and a second component, and most preferably said second component and a third component. The second component of the surfactant is characterized as
(B) an organo, hydrocarbyl, or aromatic monosulfonic acid, or admixture of such acids, having the formula ##STR3## wherein
R.sub.5 is organo, a hydrocarbyl radical, or hydrocarbon radical selected from the group consisting of alkyl, aralkyl, cycloalkyl, aryl, alkaryl, alkenyl, and alkynyl including such radicals when inertly substituted. The hydrocarbon moiety is exemplified by hydrocarbon groups which range from about one to about 30 carbon atoms, preferably from about one to about 20 carbon atoms. When R.sub.5 is alkyl, it can typically be methyl, ethyl, n-propyl, iso-propyl, n-butyl, i-butyl, sec-butyl, amyl, octyl, decyl, octadecyl, or the like. When R.sub.5 is aralkyl it can typically be benzyl, betaphenylethyl, and the like. When R.sub.5 is cycloalkyl, it can typically be cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, 2-methyl-cycloheptyl, 3-butyl cyclohexyl, 3-methyl cyclohexyl, and the like. When R.sub.5 is aryl, it can typically be phenyl, naphethyl, and the like. When R.sub.5 is alkaryl, it can typically be tolyl, xylyl, and the like. When R.sub.5 is alkenyl, it can typically be vinyl, allyl, 1-butenyl, and the like. When R is alkynyl, it can typically be ethynyl, propynyl, butynyl, and the like. R.sub.5 can be inertly substituted, i.e., bear a non-reactive substituent such as alkyl, aryl, cycloalkyl, ether, halogen, nitro, etc. The benzene ring can also be further inertly substituted. Typically inertly substituted R.sub.5 groups and ring substitutents may include 3-chloropropyl, 2-ethoxyethyl, carboethoxy-methnyl, 4-methyl cyclohexyl, p-chlorophenyl, p-chloro benzyl, 3-chloro-5-methylphenyl, etc. The preferred R.sub.5 groups are alkyl, polyalkyl, aryl, polyaryl, alkoxy, polyalkoxy, arylalkyl, or alkylaryl hydrocarbon radicals having from about 4 to about 18 carbon atoms, preferably from about 12 to about 15 carbon atoms. Preferably the substitutent hydrocarbon group is saturated or unsaturated, straight-chain or branched-chain, e.g., n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, n-heptyl, n-octyl, isooctyl, 2-ethylhexyl, isobutyl, n-nonyl, tripropylene, n-decyl, undecyl, n-dodecyl, tridecyl, n-tetradecyl, pentadecyl, n-hexadecyl, n-octadecyl, eicosyl, docosyl, vinyl, propenyl, octenyl, 10-undecenyl, 9 octadecenyl, cyclopentyl, cyclohexyl, cyclohexamethyl, and the like; and R.sub.5 is in an ortho or para position on the benzene nucleus relative to the sulfonic acid group.
Compounds of this class include, for example, aromatic monosulfonic acids wherein the benzene ring is substituted with up to five organic, or hydrocarboyl radicals, i.e., alkyl, polyalkyl, alkoxy, alkyl thio, and polyalkoxy ether radicals and the like.
Specific examples of sulfonic acids of this type include the alkyl or polyalkyl substituted benzene sulfonic acid, an alkyl substituted phenol sulfonic acid such as dodecyl benzene sulfonic acid, keryl benzene sulfonic acid, nonylbenzene sulfonic acid, dinonyl benzene sulfonic acid, trihexyl benzene sulfonic acid, nonyl phenol sulfonic acid, tetradecyl benzene sulfonic acid, and the like.
The admixture, as suggested, most preferably also includes a third component, or mixture of such components, viz.,
(C) an ammonium ion, substituted ammonium ion or alkali metal substituted organo, hydrocarbyl, or aromatic monosulfonic acid, i.e., an ammonium ion, substituted ammonium ion or alkali metal sulfonate characterized by the formula ##STR4## wherein
M is an ammonium ion, substituted ammonium ion or metal selected from Group I-A of the Periodic Table of the Elements (E. H. Sargent & Co. Scientific Laboratory Equipment, Copyright 1962), preferably sodium, and
R.sub.6 is organo, a hydrocarbyl radical, or hydrocarbon radical selected from the group consisting of alkyl, aralkyl, cycloalkyl, aryl, alkaryl, alkenyl, and alkynyl including such radicals when inertly substituted. The hydrocarbon moiety is exemplified by hydrocarbon groups which range from about one to about 30 carbon atoms, preferably from about one to about 20 carbon atoms. When R.sub.6 is alkyl, and can typically be methyl, ethyl, n-propyl, iso-propyl, n-butyl, i-butyl, sec-butyl, amyl, octyl, decyl, octadecyl, and the like. When R.sub.6 is aralkyl it can typically be benzyl, betaphenylethyl, and the like. When R.sub.6 is cycloalkyl, it can typically be cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, 2-methyl-cycloheptyl, 3-butyl cyclohexyl, 3-methyl cyclohexyl, and the like. When R.sub.6 is aryl, it can typically be phenyl, naphethyl, and the like. When R.sub.6 is alkaryl, it can typically be tolyl, xylyl, or the like. When R.sub.6 is alkenyl, it can typically be vinyl, allyl, 1-butenyl, and the like. When R.sub.6 is alkynyl, it can typically be ethynyl, propynyl, butynyl, and the like. R.sub.6 can be inertly substituted, i.e., bear a non-reactive substitutent such as alkyl, aryl, cycloalkyl, ether, halogen, nitro, etc. The benzene ring can also be further inertly substituted. Typically inertly substituted R.sub.6 groups may include 3-chloropropyl, 2-ethoxyethyl, carboethoxymethyl, 4-methyl cyclohexyl, p-chlorophenyl, p-chloro benzyl, 3-chloro-5-methylphenyl, etc. The preferred R.sub.6 groups are alkyl, polyalkyl, aryl, polyaryl, alkoxy, polyalkoxy, arylalkyl or alkylaryl hydrocarbon radicals having from about 4 to about 18 carbon atoms, preferably from about 12 to about 15 carbon atoms. Preferably the substitutent hydrocarbon group is saturated or unsaturated, straight-chains or branched-chains, e.g., n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, n-heptyl, n-octyl, isooctyl, 2-ethylhexyl, isobutyl, n-nonyl, tripropylene, n-decyl, undecyl, n-dodecyl, tridecyl, n-tetradecyl, pentadecyl, n-hexadecyl, n-octadecyl, eicosyl, docosyl, vinyl, propenyl, octenyl, 10-undecenyl, 9 octadecenyl, cyclopentyl, cyclohexyl, cyclohexamethyl, and the like; and the R.sub.6 is an ortho or para position on the benzene nucleus relative to the ammonium ion, substituted ammonium ion, or metal sulfonate group.
Exemplary of suitable ammonium or alkali metal sulfonates are the ammonium, sodium, or potassium salts of aromatic monosulfonic acids wherein the benzene ring is substituted with up to five organic, or hydrocarboyl radicals, e.g., alkyl, polyalkyl, alkoxy, alkyl thio, polyalkoxy ether radicals and the like.
Specific examples of sulfonic acid salts of this type include the ammonium or substituted ammonium salt of the alkyl or polyalkyl benzene sulfonic acid, i.e., ammonium dodecylbenzene sulfonate, triethanolamine dodecylbenzenesulfonate, sodium salt of the alkyl or polyalkyl benzene sulfonic acid, such as the sodium salt of dodecyl benzene sulfonic acid, the sodium salt of keryl benzene sulfonic acid, the sodium salt of dinonyl benzene sulfonic acid, the sodium or potassium salt of trihexyl benzene sulfonic acid, the sodium or potassium salt of nonyl phenol sulfonic acid, the sodium or potassium salt of tetradecyl benzene sulfonic acid, and the like.
In its most preferred aspects the composition of this invention includes not only the surfactant characterized in I(A), preferably I(A)+I(B), or more preferably I(A)+(B)+I(C), but also the additional presence of an oil soluble demulsifier.
(II) The demulsifier is constituted of
an ethoxylated or propoxylated, or admixed ethoxylated/propoxylated, phenol formaldehyde resin substituted at a position para to the ethoxy or propoxy group, or mixed ethoxy/propoxy groups, by an organo, hydrocarbyl or hydrocarbon group, said modified phenol formaldehyde resin being characterized as follows: ##STR5## wherein
R.sub.7 represents one or more ethoxy or propoxy groups, or mixed ethoxy and propoxy groups, and
R.sub.8 is a hydrocarbyl radical, or hydrocarbon radical selected from the group consisting of alkyl, aralkyl, cycloalkyl, aryl, alkaryl, alkenyl, and alkynyl including such radicals when inertly substituted. The hydrocarbon moiety is exemplified by hydrocarbon groups which range from about one to about 30 carbon atoms, preferably from about one to about 20 carbon atoms. When R.sub.8 is alkyl, R.sub.8 can typically be methyl, ethyl, n-propyl, iso-propyl, n-butyl, i-butyl, sec-butyl, amyl, octyl, decyl, octadecyl, and the like. When R.sub.8 is aralkyl it can typically be benzyl, betaphenylethyl, and the like. When R.sub.8 is cycloalkyl, it can typically be cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, 2-methyl-cycloheptyl, 3-butyl cyclohexyl, 3-methyl cyclohexyl, and the like. When R.sub.8 is aryl, it can typically be phenyl, ethylphenyl, and the like. When R.sub.8 is alkaryl, it can typically be tolyl, xylyl, and the like. When R.sub.8 is alkenyl, it can typically be vinyl, allyl, 1-butenyl, and the like. When R.sub.8 is alkynyl, it can typically be ethynyl, propynyl, butynyl, and the like. R.sub.8 can be inertly substituted, i.e., it may bear a non-reactive substitutent such as alkyl, aryl, cycloalkyl, ether, halogen, nitro, and the like. Typically inertly substituted R.sub.8 groups may include 3-chloropropyl, 2-ethoxyethyl, carboethoxymethnyl, 4-methyl cyclohexyl, p-chlorophenyl, p-chloro benzyl, 3-chloro-5-methylphenyl, etc. In the formula, m is an integer of 1 or greater than 1, and the molecular weight of the demulsifier, or resin, generally ranges from about 2000 to about 20,000, preferably from about 5000 to about 10,000. The resin can be unmodified, or modified as by substitution or addition of substitutents in the side chains or nucleus of the aromatic constitutents of the molecules, especially by reaction at one or both terminal nuclei.
The compounds per se characterized as I(B), I(C) and II are known. The fatty acid esters characterized as I(A) are prepared by direct esterification of 1,4-sorbitan. In the preparation of the fatty acid esters a preselected amount of the fatty acid is charged into a reaction vessel and admixed with incremental charges of the ethylene or propylene oxide, or both, at controlled temperature and pressure until substantially equivalent molar amounts of the two reactants have been reacted, and reaction is complete. For example, 4000 pounds of sorbitan monooleate is charged into a stainless steel vessel and admixed initially with 30 pounds of ethylene oxide, the reaction mixture being vented, purged of air and stirred while controlling the temperature below about 275.degree. F. and pressure of about 0-15 psig. While controlling the temperature and pressurre at these conditions, increments of the ethylene oxide are continuously added until the reaction is complete. Thus, a charge of ethylene oxide in the amounts of 5000 pounds and 4460 pounds, respectively, are placed in weigh tanks and, while controlling the temperature of between about 270.degree.-275.degree. F., the ethylene oxide is charged to the stirred reaction vessel at a rate of about 2 gallons per minute. As the temperature and pressure subside, the rate of addition of ethylene oxide is increased to about 4 gallons per minute. When reaction has been completed, and all of the ethylene oxide has been added, the reaction vessel is purged with nitrogen, and thereafter the reaction mixture is neutralized with sodium hydroxide, and the fatty acid ester separated from the reaction mixture.
The surfactant and demulsifier are prepared prior to use by dissolving one or both ingredients in an oil soluble solvent, and preferably each is separately dissolved in an oil soluble solvent and the solvent-containing additives blended together at the time they are added to the oil. Exemplary of oil soluble solvents for dissolving these additives are aromatic hydrocarbons having a single benzene nucleus, preferably aromatic hydrocarbons containing from 6 to about 9 carbon atoms, e.g., xylene, n-propyl benzene, isopropyl benzene and the like; cycloparaffin hydrocarbons which contain from 4 to about 9 carbon atoms, e.g., cyclobutane, cyclopentane, cyclohexane, cycloheptane and the like; water soluble alcohols such as propyl alcohol, isopropyl alcohol, isobutyl alcohol, sec-butyl alcohol, t-butyl alcohol and the like; aromatic alcohols such as triphenylcarbinol and the like; water soluble polyhydric alcohols such as ethylene glycol, hexamethylene glycol, glycerol and the like; or admixtures of these and/or other solvents.
The invention resides in the discovery of novel surfactants, and particularly novel admixtures of surfactants and demulsifiers for removing very finely divided particulate solids from solids-containing petroleum and syncrudes. Generally, the surfactant and demulsifier prior to use are each dissolved in a suitable solvent and each separately added, or blended together and then added, to the solids-containing whole heavy crude petroleum or syncrude, or petroleum or syncrude fraction at the site wherein the solids are to be removed from the oil. The surfactant and demulsifier are added, with water, to the solid-containing oil in concentrations adequate to remove the solids from the oil, and concentrate the solids within the water phase. Suitably, the surfactant, or surfactants, and the demulsifier, or demulsifiers, are added to the oil in concentration ranging from about 10 parts to about 5000 parts, preferably from about 30 parts to about 80 parts, per million parts by volume of oil (vppm). The ratio of demulsifier:surfactant generally ranges from about 1:1 to about 15:1, preferably from about 2:1 to about 4:1, based on the sum total volume of the surfactant and demulsifier.
It is required to form an emulsion between the two immiscible liquids, which creates a large interfacial area between the oil and water phases. The principles for the formation of oil and water emulsions are well known. The addition of a surfactant into an oil significantly lowers the interfacial tension of the oil against water due to the concentration of the surfactant at the oil/water interface and promotes emulsification between the oil and water faces. On the other hand, a demulsifier, at least to an extent, breaks the oil/water emulsion by removing the oil film from around the solids particles, and cleans the water phase of oil. In the instant situation, the surfactant of this invention cleans the surfaces of the solids of oil and aids in the transfer of solids to the water phase. The demulsifier causes the small water droplets to coalesce, and at the time cleans, or purges, the oil from the water phase. The surfactant is, in fact, outstanding in its effectiveness in wetting the solids, and cleaning the surfaces of the solids of oil, and the demulsifier is similarly effective in breaking the oil and water emulsion, and in removing and transferring oil from the water phase to the oil phase. The wetted solids are readily transferred from the oil phase to the water phase.
Water is added to the oil containing the surfactant and demulsifier, generally in concentration ranging from about 5 percent to about 50 percent, preferably from about 10 percent to about 30 percent, based on the volume of the oil. The oil and water are then emulsified, as by shearing the oil and water in a mixer. The contacting water, in the presence of the surfactant water wets and cleans the solids particles and transfers the solids to the water phase. The action of the demulsifier causes the small drops of water to coalesce and cleans the oil from the water phase. Upon gravity settling, preferably at elevated temperature which is helpful in breaking the emulsion, the solids-containing water phase cleanly separates from the oil phase. In a preferred embodiment, however, the oil and water emulsion is transported, or flowed, into an electrostatic coaleser to form a clean oil phase overflow and solids-containing water phase underflow; or where the whole heavy crude petroleum or syncrude oil, or petroleum or syncrude fraction contains a particularly high concentration of solids, the oil and water emulsion can be treated initially by gravity settling to effect partial separation of a solids-containing water phase, and the remaining emulsion and/or oil phases further treated in an electrostatic coalescer, or staged series of electrostatic coalescers.
In accordance with the best mode of practicing the process, two schemes of operation are generally employed depending upon the nature and concentration of solids contained in the oil. A first process scheme embodies treatment of an oil which contains a low to moderate amount of solids, e.g. about 2 to 6 percent solids, and a second embodies treatment of an oil which contains moderate to high concentrations of solids, e.g. about 6 to 16 percent solids.